Surface properties of nanocrystalline TiO ₂ coatings in relation to the in vitro plasma protein adsorption

Abstract

This study reports on the selective adsorption of whole plasma proteins on hydrothermally (HT) grown TiO2-anatase coatings and its dependence on the three main surface properties: surface charge, wettability and roughness. The influence of the photo-activation of TiO2 by UV irradiation was also evaluated. Even though the protein adhesion onto Ti-based substrates was only moderate, better adsorption of any protein (at pH = 7.4) occurred for the most negatively charged and hydrophobic substrate (Ti non-treated) and for the most nanorough and hydrophilic surface (HT Ti3), indicating that the mutual action of the surface characteristics is responsible for the attraction and adhesion of the proteins. The HT coatings showed a higher adsorption of certain proteins (albumin 'passivation' layer, apolipoproteins, vitamin D-binding protein, ceruloplasmin, α-2-HS-glycoprotein) and higher ratios of albumin to fibrinogen and albumin to immunoglobulin γ-chains. The UV pre-irradiation affected the surface properties and strongly reduced the adsorption of the proteins. These results provide in-depth knowledge about the characterization of nanocrystalline TiO2 coatings for body implants and provide a basis for future studies on the hemocompatibility and biocompatibility of such surfaces.

Electrokinetic behaviour of porous TiO2-coated implants

“…The streaming potential measurements showed that all the surfaces were negatively charged at physiological pH, although to a different extend according to the chemical composition and surface functionalities [3]. However, different f-values were achieved for the same substrate when calculated by Eq.…”

“…For this reason the study of the implant surface charge, in addition to the surface roughness and wettability, is fundamental to predict the kind and extent of the biological interaction during the first stage after the material insertion in the body. In a previous study [3] we showed how the abovementioned characteristics influenced the adsorption of the plasma proteins on HT TiO 2 -anatase coatings on titanium for hard tissue replacement. The HT surfaces behaved more hydrophilic than the non-treated titanium (Ti NT) and owned an additional nano-roughness, due to the nano-crystals, as evident from Fig.…”

“…The HT process steps are reported in our previous work [3]. In brief, the titanium discs were heated at 200°C for 48 h in an autoclave containing an aqueous suspension of titanium (IV) isopropoxide [Ti(iOPr) 4 , Acros Organics] at pH 10.…”

Electrokinetic Properties of TiO2 Nanotubular Surfaces

“…Together with the choice for the most suitable surface modification technique, the evaluation of the physico-chemical properties of a biomaterial surface is compulsory for the proper design of body implants and to predict a priori the influence of the material properties on the events occurring at the bio-interface [12, 13]. In fact, the surface properties are responsible for the interactions with the surrounding tissues and, influencing the “race for the surface” between cells and bacteria [14], affect the consequent acceptance of the implant.…”

Enhanced osteogenesis on titanium implants by UVB photofunctionalization of hydrothermally grown TiO2 coatings

“…We recently demonstrated by surface streaming potential studies 21 that after irradiation of the HT-anatase coatings the amount of hydroxyl groups on the surface was strongly enhanced; moreover, Han et al 13 reported that the amount of negatively charged, basic Ti-OH groups after UV irradiation was increased and the treatment helped the apatite-forming ability of the SaOS-2 cell adhesion on micro-arc oxidized Ti-surfaces. In accordance with Tengvall and Lundstrom, 46 the creation of a highly hydroxylated surface improved the HT-coating reactivity with the surrounding ions, proteins and cells.…”